Pilot multi-site quality assurance study of batch-mode clinical-scale automated xenon-129 hyperpolarizers.

We present a pilot quality assurance (QA) study of spin-exchange optical pumping (SEOP) performed on two nearly identical second-generation (GEN-2) automated batch-mode clinical-scale ¹²⁹ Xe hyperpolarizers, each utilizing a convective forced air oven, high-power (~170 W) continuous pump laser irradiation, and xenon-rich gas mixtures (~1.30 atm partial pressure). In one study, the repeatability of SEOP in a 1000 Torr Xe/900 Torr N ₂ /100 Torr ⁴ He (2000 Torr total pressure) gas mixture is evaluated over the course of ~700 gas loading cycles, with negligible decrease in performance during the first ~200 cycles, and with high ¹²⁹ Xe polarization levels (avg. %P _Xe  = 71.7% with standard deviation σ _PXe  = 1.5%), build-up rates (avg. γ _SEOP  = 0.019 min ^-1 with standard deviation σ _γ  = 0.003 min ^-1 ) and polarization lifetimes (avg. T ₁  = 90.5 min with standard deviation σ _T  = 10.3 min) reported at moderate oven temperature of ~70 °C. Although the SEOP cell in this study exhibited a detectable performance decrease after 400 cycles, the cell continued to produce potentially useable HP ¹²⁹ Xe with %P _Xe  = 42.3 ± 0.6% even after nearly 700 refill cycles. The possibility of "regenerating" "dormant" (i.e., not used for an extended period of time) SEOP cells using repeated temperature cycling methods to recover %P _Xe is also demonstrated. The quality and consistency of results show significant promise for translation to clinical-scale production of hyperpolarized ¹²⁹ Xe contrast agents for imaging and bio-sensing applications.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2020 Elsevier Inc. All rights reserved.)